I think the flippers are a very creative invention, and perfect for some people......especially those who don't sew. I prefer to sew my own liners because they function superbly, and I can sew them as needed when I remodel the cage. I enjoy the creative aspect of sewing my own custom liners and they are quite economical as well.
I generally go on a fleece-buying binge on Black Friday when I can score some real bargains. I try to anticipate my needs for the next year, and buy enough to last until the next BF sales. I, like many others here, buy my fleece at JoAnn Fabrics. Over time, I have found that the blizzard fleece is better quality and lasts longer. I made three sets of liners over a year ago and rotate them weekly. They are barely showing signs of wear.
There is no burrowing because the liners have some weight to them. They lie smooth and don't wrinkle or buckle. In my experience, towels are just about the worst fabric to use in the cage because they begin to smell almost immediately. I only use towels for lap time.